The rapidly growing body of sequenced DNA demands efficient computer programs for its analysis and storage. The program described in this paper, SEQ-ED, has been designed to handle a large number of DNA sequences up to 200 kilobases [kb] long stored in a sequence library. In order to minimize the required storage space, the sequences are stored in a compressed format using three binary digits per base. In the development of this program, special care has been given to make it easy to use for molecular biologists without any previous computer experience.